Bacterial infection of lung airways underlies some of the main complications of COPD, which impact significantly in disease progression and outcome. Acute exacerbations (AE) represent one of the major contributing factors of morbidity, clinical deterioration, and morbidity among patients with COPD. Most importantly, AE and severity of COPD are mutually interrelated as AE are more frequent with patients with more severe COPD and, conversely, cause further deterioration of the degree of airflow limitation and disease severity. Lower airway bacterial infection or colonization may be the triggering mechanism of these immunological and structural abnormalities. Novel techniques aimed at amplification and sequencing of the gene encoding the bacterial small subunit ribosomal RNA (SSU-rRNA) allow for a molecular interrogation of species of bacteria present in lung diseases, such as demonstrated in cystic fibrosis. This technique offers significant potential advantages over traditional approaches including bacterial culture of sputum, induced sputum, or bronchoalveolar lavaged sampling. In this proposal, we hypothesize that the airways of COPD patients will contain defined microbiota, which is different from that of smokers with minimal/mild disease. Furthermore, we propose that the microbiota in COPD lungs changes throughout the bronchial tree and it correlates with markers inflammation. Specific Aim 1 will determine the lung microbiota along the airways and in the parenchyma in patients with COPD, smokers with minimal or mild disease, and in normal lungs using laser-capture microdissected LTRC samples based on high throughput amplification and sequencing of the gene encoding the SSU-rRNA. Specific Aim 2 will correlate specific microbiota with tissue markers of inflammation and apoptosis in lungs of patients COPD, smokers with minimal or mild disease and normal lungs using immunofluorescence allied to quantification by planimetry and/or stereology. This proposal may lead to highly relevant data with potential impact on fundamental aspects of the normal airway microenvironment on lung immunity and the role of bacterial in the pathogenesis of COPD, with potential applications to non-COPD lung diseases. PUBLIC HEALTH RELEVANCE: Bacterial infection of lung airways underlies some of the main complications of COPD, which is a disease caused by cigarette smoke and characterized by progressive difficulty in breathing. Patients with severe COPD are at risk of getting worse and acquiring viral and bacterial infections. These are called exacerbations, which oblige patients to be hospitalized and received antibiotics and drugs that suppress the immune system. These patients are then at significantly increased risk of death and marked clinical worsening of the shortness of breath. The proposed study is a novel way to find out whether there are bacteria present in small airway tubes in patients with COPD. We propose to use the lung tissues collected by the LTRC and translate a novel and state of the art method to perform a large scale screen of the bacteria that may present in normal and diseased lungs. (End of Abstract)